ARTICLE IN PRESS JID: JTICE [m5G;August 26, 2015;8:51] Journal of the Taiwan Institute of Chemical Engineers 000 (2015) 1–12 Contents lists available at ScienceDirect Journal of the Taiwan Institute of Chemical Engineers journal homepage: www.elsevier.com/locate/jtice Various characteristics of multi-modified rice husk silica-anchored Ni or Pt nanoparticles as swift catalytic systems in some petrochemical processes Salah A. Hassan a , Ahmed M. Al-Sabagh b , Nasser H. Shalaby b,∗ , Samia A. Hanafi b , Hamdi A. Hassan a a Department of Chemistry, Faculty of Science, Ain Shams University, Abbassia, Cairo, Egypt b Egyptian Petroleum Research Institute, Nasr City 11727, Cairo, Egypt article info Article history: Received 20 March 2015 Revised 20 July 2015 Accepted 7 August 2015 Available online xxx Keywords: Rice husk silica xerogel Textural tuning Surface-functionalized silica Nano-catalysts Anchored Ni and Pt nanoparticles Ethanol dehydrogenation abstract Considering the local rice husk (RH) as a renewable source for production of value added silica, new swift catalysts based on the extracted silica (RHS) were designed in this work. RHS was texturally tuned by us- ing both CTAB (cationic surfactant) and Span40 (nonionic surfactant). Surfaces of RHS xerogel and CTAB- templated RHS were functionalized with mixed 3-aminopropyltriethoxysilane and triethoxymethylsilane for in situ anchorage of Ni or Pt nanoparticles. Ni nanoparticles were also immobilized onto Span40-templated RHS surface through dual tuning effect. The as-synthesized samples were characterized via N 2 physisorp- tion, H 2 chemisorption, XRD, FTIR, TEM and TGA-DSC techniques and applied in ethanol dehydrogenation at different temperatures. Anchored Ni nanoparticles were embedded in the protecting organo-functionalized silica monolayer in a uniform dispersion profile, displaying higher dehydrogenation activity and stabilized performance with reaction time-on-stream for selective production of acetaldehyde (77.8 and 63.6% over F-SG-Ni and F-CTAB-MS-Ni, respectively). Attached Pt nanoparticles to pendant amine groups of functional- ized RHS xerogel surface appeared in spherical shapes of larger average sizes with low edges and corners. They tended to aggregate in nanocrystallites with distorted tetrahedral (111) facets of damped and less stabi- lized catalytic performance to produce only 17.3% acetaldehyde. Span40-templated RHS-Ni exhibited lower activity to produce 53.3% acetaldehyde, although with high selectivity comparable with RHS-Ni. © 2015 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved. 1. Introduction Numerous reviews [e.g., 1–6] have been dedicated to rice husks (RH), produced in large quantities as waste in rice milling indus- try, and different products obtained from their thermal degradation at different conditions. Although the uncontrolled burning of rice husks causes serious pollution problems, their controlled burning in air leads to production of white rice husk ash (WRHA) containing almost pure silica (RHS, 95%) in a hydrated amorphous form, with high porosity and reactivity. The amorphous structure of RHS makes it “flexible silica” which can be used as an excellent starting base for synthesis of several important materials such as silicon tetrachloride [7], magnesium silicide [8], sodium silicate [9], zeolites [10,11], etc. For using the rice husk silica (RHS) as catalyst support with advanced properties, it can be texturally modified by using organic templates, ∗ Corresponding author. Tel.: +20 222745902; fax: +20 222747433. E-mail address: chem.shalaby@gmail.com, nasser.shalaby@yahoo.com (N.H. Shalaby). e.g., CTAB, to obtain mesoporous silica of higher surface area and con- trolled pore sizes [12]. Other organic templates were also used for controlling morphology and particle size, e.g., p-amino benzoic acid and p-phenylenediamine [13] and sorbitan monolaurate (span 20), sorbitan monopalmitate (span 40) and sorbitan monostearate (span 60) [14]. Silica-based materials often suffer from poor hydrothermal stability in humid environment or basic conditions. For instance, 3- aminopropyl-functionalized silica was often not stable enough for technical processes [15,16]. One of the approaches to overcome this limitation is to functionalize silica surface with a second group to protect it against unwanted hydrolysis. Silica functionalized with a mixture of chloropropyl and methyl groups as an example was hy- drothermally more stable than that functionalized with chloropropyl alone [17]. This way could allow adjusting the amount of active 3- aminopropyl species on the surface, recalling controlled and defined chemical environment, as a prime requirement in heterogeneous catalysis. Recently, several methods were described for tailoring func- tional nanomaterials containing specific, predictable nanostructures whose chemical composition or interfacial structure enables them to perform a specific job [18]. Following these methods, surface http://dx.doi.org/10.1016/j.jtice.2015.08.001 1876-1070/© 2015 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved. Please cite this article as: S.A. Hassan et al., Various characteristics of multi-modified rice husk silica-anchored Ni or Pt nanopar- ticles as swift catalytic systems in some petrochemical processes, Journal of the Taiwan Institute of Chemical Engineers (2015), http://dx.doi.org/10.1016/j.jtice.2015.08.001